The iron trains of Mauritania

At almost 2.5km long, Mauritania's iron trains are some of the longest in the world. [Daniel Rodrigues/Al Jazeera]

At nearly 2.5km in length, the iron trains of Mauritania are among the longest in the world.

Their journey extends between Zouerat - the largest town in the country's north, known for its iron ore mining industry - and the port city of Nouadhibou in the west, for a total distance of 652km. The trip, which cuts through the heart of the Sahara desert, can last as little as 16 hours if the train is empty of ore, and up to 20 hours if the cars are full.

Impoverished locals often risk jumping on to the train's cars to travel between towns to visit relatives. Sometimes, the trains also transport goods such as live animals or fruit.

High daytime temperatures and very low night-time temperatures complicate the journey, as does the dust produced by the more than 200 train cars, each carrying 84 tonnes of iron ore.

Travellers willing to pay can buy tickets for about $3 to board the last car of the train, offering some comfort, although most of these passenger cars are a half a century old and not cleaned frequently.

Locals sometimes use the trains to transport animals or goods. [Daniel Rodrigues/Al Jazeera]

People load apples onto the train on its return journey to Zouerat, a northern Mauritanian town known for its iron ore mining industry. [Daniel Rodrigues/Al Jazeera]

The journey can take up to 16 hours when the cars are empty. Some passengers take advantage of this time to nap. [Daniel Rodrigues/Al Jazeera]

High temperatures during the day and very low temperatures at night can make for a difficult journey. [Daniel Rodrigues/Al Jazeera]

In Zouaret, the final destination, goats are unloaded from the train. [Daniel Rodrigues/Al Jazeera]

For those who are able to pay $3, a passenger car is available at the end of the train. [Daniel Rodrigues/Al Jazeera]

Passengers fill a car carrying iron ore for the 20-hour journey to Nouadhibou. Travellers cover the ore with sheets to reduce the dust it produces when the train is moving. [Daniel Rodrigues/Al Jazeera]

Travellers catch the train between Nouadhibou and Zouerat to visit family members along its route. [Daniel Rodrigues/Al Jazeera]

The train, laden with iron ore, travels through the Sahara to the port of Nouadhibou on the western edge of Mauritania. [Daniel Rodrigues/Al Jazeera]

People sitting on top of the ore find themselves covered in dust soon after the journey begins. [Daniel Rodrigues/Al Jazeera]

Animals and livestock are often loaded on to the train. [Daniel Rodrigues/Al Jazeera]

The journey through the desert continues into the cold, dark hours of night. [Daniel Rodrigues/Al Jazeera]